Nu-hydroxy-2-pyridinethiones and method of preparing same



Patented Aug. 17 1954 'N-HYDROXY-2-PYRIDINETHIONES AND METHOD OF PREPARING SAME Elliott N. Shaw, New York, N. Y., and Jack Bernstein, New Brunswick, N. J., assignors to Mathieson Chemical Corporation, New York, N.Y.,acorporation of Virginia No Drawing. Application January 9, 1953,

. Serial No. 330,576

application is a continuation in-part of Qur'application Serial No. 159,646, filed May 2,

1950, now abandoned.

. t This if vention relates to, and has for its object thejprovision of: [A] pyridinethiones of the generalformula l y I R v N s AH wherein R represents a member of the group con- "sisting of hydrogen, lower alkyl, (lower alkyD- oxyand halo; [B] alkali salts thereof, i. e., alkalimetal (including ammonium) and alkaline-earthe metahsalts of these pyridinethiones; [C] methods of preparing these compounds; and [D] novel J intermediates formed in these methods. The pyridinethiones A, salts B, and certain of the intermediates D arevaluable chemotherapeutic agents; l 6

Compounds of the above general formula may be in tautomeric equilibrium with the corresponding N -oxide, i. e.

"wherein R represents suchas I or by a name such as N-hydroxy-2 pyridinethione.

Thefcompounds of this invention may be ob: tained by converting acompoundof the general .iq m la W l III R N (halogen) into the correspondingfN-oxide, R. representing the group indicated hereinbefore, and reacting "the N-oxide formed with a Ineinberof the group consisting of alkali-metal sulfides, alkali-metal hydrosulfides, and thioureaP-preferably byre- .acting the N-oxide with an alkali metal hydrosulfide in water; and where the alkalisalts are desired, .by reacting the resulting pyridinethione with the appropriate baseQeQ gLsQdium carbonate.

in Claims. (01. 260-2943) The novel intermediates formed in accordance with this invention are comprised by the general formulae Irv R N (halogen) R representing the group indicated hereinbefore. These intermediates are recoverable in. the form of their acid-addition salts, especially hydrohalides.

The N-oxides of the general Formula IV hereinbefore may be obtained by reacting a compound of the general Formula III hereinbefore with a per-acid, such as perbenzoic acid or peracetic acid.

The compounds of this invention are active against a wide group of microorganisms, as indicated by the following in vitro spectrum of the representative sodium salt of N-hydroxy-2-pyridinethione:

TABLE I Antibacterial spectrum Organism: M. I. C. in pg/ml.

M icrococcus pyogenes var. aureus 209P- 0.13 Klebsiella pneumoniae 1.5

Pseudomonas aeruginosa 4.0 Streptococcus faecalisu; 0.5 Shigella dysenterzae"; 0.5 Streptococcus pyogenes C-203 0.25 Salmonella schottmitlleri 2.5 Aerobacter aerogenes "3.5 Escherichia coli 2.5 Proteus valgarzs 0.7 Mycobacterium tuberculosis var. bo'uz's Strain BCG 0.006 Salmonella typhosm. 1.5 Lactobacillus acidophilus 0.4 C'lostridium septicum 0.4 Brucella abortus 0.4 Neisseria catarrhalis 0.6 Corynebacteriam pyogenes 0.3 Streptococcus ayalactiae 0.08

Bacillus subtz'lis 0.06

TABLE II Antzfungal spectrum M. I. C. in ag/ ml. of agar Aspergillus niger 0.6 Aspergillas famz'gatas 0.3 Penicillum notatam -1 0.3 Ceratostomella uZmLi 0.08 Trichophyton mentogrophytes No. 1920 1 Trichophyton mentogrophytes Squibb 0.15 T. tonsurans 1. T. rubram 1 T. schoenleim' 0.5. T. m'olaceoam 2 T. faviforme var. discoides 0.03 T. fa'uiforme var. ochraceam 0.03 Microsporum audoaim' 0.3 M. audouini (Kligman strain) 0.06 M. cam's 1 Epidermophyton flocossum 0.25 Sacch. cerevisiae 0.08 S. pastorianus 0.04 Candida albicans 0.08 0.10-

Cryptococcus neoformans Illustrating utilization of the compounds of this invention as chemotherapeutic agents, the sodium salt of N-hydroxy-2-pyridinethione may be formulated and used as follows:

Chemotherapeutic nasal decongestant solution,

containing per cc. water:

50-100 gamma sodium salt of N-hydroxy-2- pyridinethione 2.5 mg. phenylephrine hydrochloride Phosphate buffer (to about pH '7) Chlorbutanol (as preservative) corrected, and all solutions referred to without identification of solvent being solutions in water:)

EXAMPLE 1 Preparation of N -hydrory-2myridinethione (a) 35 g. 2-bromo-pyridine is added to a solution of 38 g. perbenzoic acid (20% molar excess) in 600 ml. chloroform, and the solution is allowed to stand for 4 days. The reaction mixture is then extracted three times with 150 ml. portions of 20% hydrochloric acid solution, and the (combined) acid extract is evaporated to dryness in vacuo. The residue (2-bromo-pyridine-N oxide hydrochloride) is recrystallized from alcohol-ether, yielding about 28 g. of 'the product melting at about 135-136" C.

(b) A solution of 3.3 g. 2-bromo-pyridineN- oxide-hydrochloride in 5 ml. water is heated on. a steam bath while a solution of 4.1 g. sodium sulfide nonahydrate in ml. water is added in 3 portions at 20-minute intervals. After heating for an additional half hour, the reaction mixture is cooled and acidified to Congo red with 20% hydrochloric acid solution, yielding 1.1 g. of a solid precipitate melting at 68-70 C. The precipitate is dissolved in 10 ml. normal sodium hydroxide solution; and the solution is filtered free of a small amount of sulfur and slowly acidified to Congo red with normal hydrochloric acid solution. The product (N hydroxy 2 pyridinethione) is obtained as colorless crystals melting at about 68 C. in a yield of about 0.68 g. [It is noted that this product may also be named lhydroxy-2- (1H) pyridinethione] [Alternatively, the 2-bromo-pyridine-N-oxlde hydrochloride intermediate is obtained as follows: 150 g. 40% peracetic acid (peracetic in acetic acid) is added slowly to '79 g. 2-bromopyridine, while maintaining the temperature below 15 C., and such temperature is maintained for an additional hour. The reaction mixture is then heated to 45-50 C. or 24 hours, and concentrated to half volume at 2-3 mm. (bath tempera- .ture 30 C.), and the residue is poured onto cracked ice, made strongly alkaline with 40% potassium hydroxide solution at 5 C., and then extracted three times with 300 ml. portions of chloroform. The (combined) chloroform extract is then extracted three times with 300 ml. portions of 20% hydrochloric acid solution, and the (combined) aqueous extract is concentrated to dryness under reduced pressure. The residue, after recrystallization from alcohol-ether, weighs about 61 g., melts at about 127-130 C., and shows no depression of melting point with 2-bromopyridine-N-oxide hydrochloride obtained as described in a.]

EXAMPLE? 2 Preparation of N -hydrory-3-etho;ry-2- pyridinethione (a) A solution of 28 g. 2-bromo-3-ethoxypyridine hydrobromide in 200 ml. water is made strongly alkaline by addition of 40% potassium hydroxide solution, and the free base formed is extracted three times with 150 ml. portions of chloroform. The (combined) chloroform solution is dried, and added to a solution of 16.6 g. perbenzoic acid in 300 ml. chloroform; and the reaction mixture is allowed to stand at room temperature for 3 days, and then extracted three times with 150ml. portions of 20% hydrochloric acid solution. The (combined) aqueous extract is concentrated to dryness under reduced pressure, yielding about 13 g. of 2-bromo-3-ethoxypyridine-N-oxide hydrochloride melting at about 158-160 C. On recrystallization from ether, the melting point of the product is raised to about 159-160 C.

(b) A solution of 30 g. 2-bromo-3-ethoxypyridine-N-oxide hydrochloride in 200 ml. water is neutralized with 25% sodium hydroxide solution; and to this solution is added a solution of 20g. of sodium hydrosulfide in ml. water while heating on a steam bath. The reaction mixture is heated for 1 hour, and filtered; the filtrate is cooled and acidified to Congo red with 20% hydrochloric acid solution; and the crystals formed (NhydroXy-3-ethoxy-2-pyridinethione) are recovered by filtration. About 19 g. of the product is obtained, melting at about 97-100 C. On recrystallization from aqueous alcohol, about 17.5 g. of a product melting at about 101-103 C. is obtained.

EXAMPLE. 3

Preparation of N-hydroccy-5-bromo-Z-pyridinethione tion; and the (combined) aqueous extract is conabsolute alcohol,

acecrzse centrated to drynessnyielding; about 4.5 g. of 2,5- dibromo-pyridine-N-oxide hydrochloride melting at aBoutdSI-IGT C. On recrystallization from the melting point 'ofthe product reaction mixture is then filtered and cooledi the drochloric acid solution and the precipitate (N- hydroxy--bromo-2-pyridinethione) is recovered The product, obtainedinua yield of about 1 g., melts at about 120-123" Cji; and on recrystallization from aqueous alcohol, about 600 ml. of a product melting at about 130-131 C. is obtained.

Mslufie l 9 3 -8 r z-b bmer3rme pyridine in 50 ml. chloroform is added to a solution of 39.4 g. perbenzoic acid in 1300 ml. chloroform. After standing at room temperature for 3 days, the reaction mixture iis extracted three times with 300 ml. portions of hydrochloric tract is concentrated to dryness under reduced pressure, yieldinerahqliti 33 e, Z-bromo-3-methy1- ...Dyridine-N-oxidehydrochloride, melting at about 177-1 79 C. with decomposition. On recrystalat about 1'79-l8 Qj1C; with decomposition. (b) Asolution of 8.5 g. 2-bromo-3-methylpyridine-N-oxide hydrochloride in 50 ml. water is neutralized with sodium hydroxide solution, and a solution of 75g. sodium hydrosulfide (70%) in 50 ml. water is added thereto, and the reaction mixture is heated for an hour on a steam bath. The reaction mixture is then filtered and cooled; and thefiltrate is acidifiedtoCongo red with ydrochloric acid solution, yielding wabout,=;2.8 gydrOXt3:methyl-2-pyridine thionewmeltingat about 71-73, C. On recrystallization from aqueous alcohol, the ,product melts 4 PL J (a) A solution of 20.8i g. ,t2-bromo-4-methyl-.. pyridine in 50 ml. chloroform is added to a solution of 23 g. perbenz'oic acid in 400 ml. chloroform, and the reaction mixture is allowed to stand at room temperature for 3 days. The solution is then extracted three times with 100 m1. portions under' reduced pressure, yielding about 22 g. 2- bromo-4-methyl-pyridine-N oxide hydrochloride melting at about"138-1"41 C. onrecrystallization from absolute alcohol, about 16.5 g. of a product melting at about 14'7- 148" C. is obtained.

(b) A solution of 16.5 g 2-bromo-4-methylpyridine-N-oxidehydrochloride in ml. water is neutralized with 25% sodium hydroxide solution, and a solution of 11.8 g. sodium hydrosul-" fide (70%) in 30 ml water isaddedthereto por- T I an h i a team ba fi t r d a eled:

' and the filtrate is a dified 0 Congo red with 201% yielding about-es.

hydrochloric acid solut' Preparation of ing for 4 days. theireaction mixture is extracted three times with 300ml. portions of 20%'hydrochloric acid solutiom'andrtlie (combined) acid extract is concentrated to dryness under reduced pressure, "yielding about 36 g. 2 -bromo-5-rnethylpyridine-N-oxide hydrochloride meltingsat about 145-148 C. On recrystallization from absolute alcohol, the product melts at about Mir-142 C." r

(b) A solution of: 6 gs2-br0md-5-methy1-pyri- .dine-Noxide hydrochloride in r "ml.- water is neutralized with 25% sodium hydroxidersolution,

g1 anda solutionof 43 g. sodium hydrosulfide"('70%) acid Solution; and the (combined) aqueous exmatioar o -a s u e a co ol r c produ meits of 20% hydrochloric acid solution and the (combilled) acid extract is concentrated to dryness recrystallization firom; aqueous alc in:;50;ml. water is added thereto; and 'the'reac- "tion mixture is heated? for" an": hour on "a ste'am bath. The'reaction' mixtureijis then filtered, and

' cooled; and the filtrate is acidified to Congo red with201% hydrochloric. acid "solution; yielding about 2 g. N-hydroxy-5 -inethyl-2 pyridinethione melting at about 101-1'04 C; On recrystallization from aqueous alcohol. the-product melts at about 106-107 c. 1

w EXAMPiL r Preparation of N-hydroxy-o-methyl-z-pyridine- Qtion of 42 g. perbenz'oic acid in 625 jrnLphloroterm, and the reaction mixture is allowed to standfatfroom temperature for-3 days; I Thereaction mixture is then extracted three times with 300 mLportionsof 20% hydrochloricacid solution; and the (combined) acid extract is concentrated "to dryness under reduced pressure, yielding about 34 gl 2+bromo-6 methy1-pyridine-N-, oxide hydrochloride melting at about 185-186 C with "decomposition! M On recrystallization: iron; absolute alcohol, theproductf melts at. about=l8 5- .solutionpf 21 ,.g.;.2-bromo 6-methyl;pyridine-N-oxide hydrojchloride in 150. ml water is neutralized with 25 aqueous sodium hydroxide solution; and a solution 0f 15 g. sodium hydrosulfide, (70 1 in -ml, water ,is. added there- .to, and the, reactionmixture is :heated for, an hour on a steam 1 bath. The reaction mixture, is

then; filtered, and cooled; and the filtrate is acidifled to Congo red with 29%. hydrochloric acidusolution, yielding about 6.1 g, lihydroxyfi-methyl- Z-pyridinethione melting at-about 51-54 C. On

ohol, therplfodmo me ts h0ut. 4?;C.--r M Alternativepreparationcog N-hydroxy' -z p i i dinethione alcohol and a solution of 19.4,.g, g p o p idine-N-oxide hydrochloride [obtainedas described solution is allowed to stand for 4 hours. lution is then made just acid to Congo red with .in Example 1-.

- (b) A solution of 10 g. sodium carbonate in 125 ml. water is added to 12.5 g. of the product obtained in (a) of this example, and the resulting The so- 20% hydrochloric acid solution, and the resulting precipitate filtered off. The precipitate, N hydroxy-Z-pyridinethione, weighs about 5 g. and melts at about 65-6'7 C.; and the absence of melting-point depression indicates it to be identical with the product obtained as described Other compounds of the general Formula I hereinbefore may be obtained by starting with the appropriate reactant (of general Formula III hereinbefore) in theprocedure of the foregoing examples. Thus obtainable are compounds: where R is a lower alkyl other than methyl (ethyl, propyl, inter alia); where R is a (lower alkyl) -oxy other than ethoxy (methoxy, for example) or is a (lower alkyl) oxy in position i, 5 or 6; and where R is chloro, for example, or is a halo in position 3, 4, or 6.

EXAMPLE 9 18.6 g. sodium carbonate monohydrate is dissolved in 500 ml. water, and 38.6 g. N-hydroxy- 2-pyridinethione is added; the reaction mixture is agitated to otain complete solution, and filtered; and the filtrate is freeze-dried. The sodium salt of N-hydroxy-Z-pyridinethione obtained in quantative yield gives the following analysis: C, 40.12;

H, 2.95; and Na, 15.34.

Sodium bicarbonateor sodium hydroxide may be used in place of the sodium carbonate.

EXAMPLE 1 0 A suspension of 1.27 g. N-hydroXy-2-pyridinethione and 0.856 g. barium hydroxide in 150 ml. Water is agitated at room temperature until complete solution occurs; and the solution is freeze dried, yielding about 2 g. of the barium salt of N-hydroxy-2-pyridinethione EXAMPLE 1 1 12.7 g. N-hydroxy-Z-pyridinethione is added to a solution of 6.9 g. potassium carbonate in 120 ml. water, and the resulting solution is freeze-dried, quantitativelyyielding the potassium salt of N-hydroxy-2-pyridinethione.

EXAMPLE l2 8 EXAMPLE 13 A suspension of 1.41 g. N-hydroxy-4-methyl- 2-pyridinethione and 0.375 g. calcium hydroxide in ml. of water isagitated at room temperature until complete solution occurs; and the solution is freeze-dried, quantitatively yielding, the calcium salt of N-hydroxy-4-methyl-2-pyridinethione. g

The invention may be variously otherwise embodied within the scope of the appended claims.

We claim:

1. Compounds of the group consisting of:fcompounds of the general formula. I r

wherein R represents a member of the group consisting of hydrogen, lower alkyl, (lower alkyl)- oxy and halo; and alkali salts thereof.

2. Compounds of the general formula (lower alkyl) 3. N-hydroxy-2-pyridinethione. 4. The sodium salt of N-hydroxy-Z-pyridinethione.

5. The method which comprises interacting a compound of the general formula R lll (halogen) R representing a'member of the group consisting of hydrogen, lower alkyl, (lower alkyD-oxy and halo, with a member of the group consisting of alkali-metal sulfides, alkali-metal hydrosulfides, and thiourea, by heating in a solvent for'the reactants, and recovering the reaction product;

6. The method which comprises interacting a compound of the general formula I R 111 (halogen) l o R representing a member of the group consisting of hydrogen, lower alkyl, (lower. alkyD-oxy and halo, with an alkali-metal hydrosulfide, by heating in water, and recovering the reaction product. 7. The method which comprises interacting compound of the general formula v I R If (halogen) R representing a member of the group consisting of hydrogen, lower alkyl, (lower alkyD-oxy and halo, with thiourea, by'heating in alcohol, and recovering the reaction product. p

9 10 8. An acid-addition salt of a compound of the sisting of hydrogen, lower alkyl, (lower alkyl)- general formula oxy, and halo.

10. An alkali salt of N-hyclroxy-2-pyridinethi one. R 5 References Cited in the file of this patent N (halogen) 1 UNITED STATES PATENTS wherein R represents a member of the group con Number Name Date 6 8 sisting of hydrogen, lower alkyl, (lower alkyl)- 10 L753 5 Kochendoerfer Apl 1900 oxy, and halo. OTHER REFERENCES 9. An acid-addition salt of a compound of the Thirfle C s 1 8, pp 342-3, 194 general formula Ital, Chem. Abstn, vol. 44, p 4473-4, (1950).

R /NH r O NH:

wherein R represents a member of the group con- 

1. COMPOUNDS OF THE GROUP CONSISTING OF: COMPOUNDS OF THE GENERAL FORMULA 